Abstract B029: LSD1-HDAC6 dual inhibitor JBI-802 is an epigenetic modulating agent with a novel mechanism of action that target MYC amplification in multiple neuroendocrine tumor types
Authors: Dhanalakshmi Sivanandhan, Sridharan Rajagopal, Chandru Gajendran, Naveen Sadhu, Mohd Zainuddin, Ramachandraiah Gosu, Luca Rastelli
Journal: Cancer Research (2022)

Abstract MYC is considered a master regulator of human cancers by modulating the transcription of numerous cancer-related genes. MYC amplification is reported in about 15% of all human cancers and is generally associated with poor prognosis and resistance to treatments. Focal amplification of MYC together with mutation in RB1 and p53 is an important event in the metastatic process of neuroendocrine tumor development. While limited options are available for direct targeting, transcriptional modulation via epigenetic modulating agent could be an attractive and viable option to target neuroendocrine cancers. JBI-802 inhibits the transcriptional regulator coREST via its component LSD1/HDAC6 therefore blocking neuroendocrine transdifferentiation and inducing cell death resulting in activity against neuroendocrine tumors. At the same time, this molecule has shown a good safety profile in toxicological studies. We have now identified a novel aspect of JBI-802 mechanism of action, the ability to induce downregulation of MYC RNA and degradation of MYC protein both in vitro and in animal models of two neuroendocrine tumors, small cell lung cancer and neuroendocrine prostate cancer JBI-802 showed significant anti-proliferative activity (0.2 to 1 µM) against several cancer cell lines as shown by Alamar blue or CTG assays. Sensitive ones included small cell lung cancer (SCLC), gastric cancer, breast cancer cell lines with RB1 mutation. Interestingly, dual inhibitor JBI-802 was also active in cell lines with MYC over-expression, while LSD1 selective inhibitors have been reported to be inactive in these cell lines. JBI-802 also inhibited MYC at RNA as well as protein level in hematological and solid tumors as assessed by RT-qPCR at RNA level and by Western blotting at protein level, while single agent LSD1 and HDAC6 inhibitors did not show significant modulation. JBI-802 also showed strong tumor growth inhibition of these tumors in mouse xenograft models. MYC levels showed a dose dependent inhibition in these tumors when tested at the end of the study. Only dual inhibition of both LSD1/HDAC6 with JBI-802 as opposed to single target inhibition is able to effectively downregulate MYC level and achieve efficacy in MYC amplified models in vivo and in vitro. This novel mechanism increases the potential population of neuroendocrine patients that could be sensitive to this compound, going beyond the proof of principle already established preclinically and clinically by single target LSD1 inhibitors. Therefore, by targeting 2 major pathways in neuroendocrine tumor development, JBI-802 novel mechanism of action is uniquely suited for the treatment of high unmet neuroendocrine tumors like small cell lung cancer, neuroendocrine prostate cancer and advanced, MYC amplified tumors. Based on this rationale, JBI-802 is being tested in phase 1/2 clinical trial focus on this type of tumors. Citation Format: Dhanalakshmi Sivanandhan, Sridharan Rajagopal, Chandru Gajendran, Naveen Sadhu, Mohd Zainuddin, Ramachandraiah Gosu, Luca Rastelli. LSD1-HDAC6 dual inhibitor JBI-802 is an epigenetic modulating agent with a novel mechanism of action that target MYC amplification in multiple neuroendocrine tumor types. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr B029.